stmhal/file: For self-contained usecase, don't define global types.

If MICROPY_VFS_FAT is defined, mp_type_fileio & mp_type_textio won't be
defined, as these may be alredy defined elsewhere. The idea is to have
compartmentalized VFS FatFs class, which can work in parallel with some
other "main" filesystem. E.g., for unix port, mp_type_fileio, etc. will
be defined for the main POSIX filesystem, while stmhal/file.c will be
a self-contained VFS file class.

stmhal/file.c

@@ -33,6 +33,11 @@
 #include "lib/fatfs/ff.h"
 #include "file.h"
 
+#if MICROPY_VFS_FAT
+#define mp_type_fileio fatfs_type_fileio
+#define mp_type_textio fatfs_type_textio
+#endif
+
 extern const mp_obj_type_t mp_type_fileio;
 extern const mp_obj_type_t mp_type_textio;